1. Field of the Invention
The present invention relates to an ATM telecommunications system adapted for the transmission of IP data over ATM and methods of transmitting IP data over an ATM transmission system.
2. Discussion of the Background
The Internet Engineering Task Force (IETF) and ATM Forum have defined several methods that aim to provide shortcuts between IP end-systems across Logical IP System (LIS) boundaries. Examples of such methods are Classical IP, Next Hop Resolution Protocol, Multi-protocol Over ATM, IP switching, Cell switching router, Tag switching, etc. However, none of the methods defined so far utilizes the inherent Quality of Service capability of the ATM network. Furthermore, most of these methods require additional complex control protocols that are difficult to manage. Overall, this means increased investment and management cost for network operators.
It is an object of the present invention to provide a very simple and scaleable architecture which gives a substantially optimal solution for an IP over ATM network service.
It is a further object of the present invention to:
exploit the QoS of the ATM network;
provide shortcut communication when necessary;
reduce connection setup delay; and
smooth migration from the current deployments;
while retaining simplicity.
The present invention introduces three additional functions to the normal operation of the Classical IP model in order to achieve the aforementioned objectives, namely:
(1) flow classification/detection;
(2) explicit indication of ATM address and QoS, to the receiver, prior to connection setup; and
(3) receiver initiated connection setup.
The present invention also provides, a multi-cast architecture based on an extension to the Multi-cast Address Resolution Service (MARS) architecture known from IETF. The proposed architecture can be implemented on end-systems as well as in routers. The latter enables smooth and transparent migration towards shortcuts without impacting end-systems. However, this can be regarded as an open implementation issue.
The present invention provides a method via which IP based end-systems that are attached to an ATM network can establish a direct uni-cast connection, even if they belong to different Logical IP Systems (LIS). In a classical IP based operation, only end-systems that belong to the same sub-net (i.e. end-systems that have a common network prefix) can communicate directly. Communication between end-systems that belong to different LISs is only possible through one, or more, routers. In order to send an IP packet to an ATM network, a communication path has to be established, which in turn requires resolution of IP addresses to ATM addresses, in advance. In a wide area network such as ATM with hundreds, or thousands, of end-systems connected to it, communication between end-systems may require multiple router hops. The address resolution process and the signaling procedure between each hop will cause unacceptable delays for many applications. In addition, establishing logical circuits for small flows, e.g., ping, DNS query, may cause scaleability problems and unnecessary overheads.
Much effort has recently been spent by standardization bodies and different for a to remedy the aforementioned problem. Most notably the Internet Engineering Task Force (IETF) has defined a method, currently an RFC draft under the name Next Hop Resolution Protocol (NHRP), that provides a shortcut for direct communication between IP end-systems belonging to different sub-nets, or LISs. However, even the current NHRP protocol fails to address the following problems:
1. Reduction in the number of open connections, or virtual circuits, in a WAN;
2. Reduction in the connection setup delay; and
3. Explicit indication of ATM addresses and Quality of Service
Other known solutions like IP switching (from Ipsilon), Cell switching router (from Toshiba), or Tag switching (from Cisco), require either control architectures and protocols which are too complex, or they lack QoS support.
The present invention addresses the three aforementioned problems. Point (1) is solved by the use of flow detection, point (2) is solved by providing receiver initiated connection setup and point (3) is solved by means of the provision of explicit indications of QoS parameters in a special control message to help the receiver to require the appropriate traffic and QoS.
According to a first aspect of the present invention, there is provided an ATM transmission system, adapted for the transmission of IP data, having at least two end-user terminals and a plurality of routers, said ATM transmission system including at least two LISs and adapted to handle both intra-LIS and inter-LIS traffic, characterized in that first connection means are provided to establish a first communication path for short lived transmissions, between first and second end-user terminals, on a hop-by-hop basis, in that signaling means are provided for exchanging call connection messages between said first and second end-user terminals over said first communications path, in that second connection means are provided to establish a second, direct, communications path, by-passing said routers between said first and second end-user terminals, and in that long lived data transmissions are transmitted over said second communications path.
Said first communications path may be a pre-established default path.
Said first end-user terminal may be a call initiating terminal, and said first end-user terminal may include signaling means for transmitting a control message to said second end-user terminal over said default path, said control message containing, inter alia, an ATM address for said first terminal and QoS parameters for said first terminal.
Said second end-user terminal may have check means for checking, on receipt of a control message from said first terminal, that said second end-user terminal has sufficient available resource to handle transmission from said first terminal, and said second connection means may establish said second communications path, if said second terminal has sufficient available resource.
Said second end-user terminal""s signaling means may transmit a message containing an error code, to said first end-user terminal, in the event that said second end-user terminal has insufficient resource to handle transmission from is said first terminal.
Short lived intra-LIS data transmissions may be transmitted over a pre-established default path established by a call initiating end-user terminal.
Long lived intra-LIS data transmissions may be transmitted over an SVC established by a call initiating end-user terminal.
Short lived inter-LIS data transmission may be transmitted over said first communications path.
End-user terminals may have data detector means for detecting data flows and classifying data flows as one of:
short lived intra-LIS;
long lived intra-LIS;
short lived inter-LIS; or
Long lived inter-LIS.
ATM VCs may only be established for the transmission of long lived data flows.
Short lived data flows may be transmitted over a system default path by-passing address resolution and connection set-up procedures.
IP data may be transmitted over said first communications path prior to establishment of said second communications path.
An end-user terminal, or router, may have multiplexing means for multiplexing a plurality of connections over a single VC.
Said routers may include processor means for processing control messages.
Control messages may be processed in:
a router;
an ARP server; or
an end-user terminal.
Said system may be adapted to support multi-casting based on the IETF MARS model.
According to a second aspect of the present invention, there is provided an end-user terminal adapted for use with an ATM transmission system as claimed in any previous claim, characterized in that said end-user terminal includes first connection means for establishing communications paths for short lived transmissions, a second connection means for establishing communications paths for long lived transmissions by-passing routers, signalling means for exchanging call connection messages, check means for checking, on receipt of a control message, said end-user terminal""s available resource, and data detector means for detecting and classifying data flows.
According to a third aspect of the present invention, there is provided a method of transmitting IP data over an ATM transmission system having at least two end-user terminals, a plurality of routers and at least two LISs, said method adapted to handle both intra-LIS and inter-LIS traffic, characterized by:
for long lived inter-LIS transmissions between a first end-user terminal and a second end-user terminal, first establishing a first communication path for short lived transmissions, between said first and second end-user terminals, on a hop-by-hop basis;
exchanging call connection messages between said first and second end-user terminals over said first communications path;
establishing a second, direct, communications path, by-passing said routers, between said first and second end-user terminals; and
transmitting long lived data transmissions over said second communications path.
Said first communications path may be a pre-established default path.
Said first end-user terminal may be a call initiating terminal, and said first end-user terminal may transmit a control message to said second end-user terminal over said default path, said control message containing, inter alia, an ATM address for said first terminal and QoS parameters for said first terminal.
Said second end-user terminal may, on receipt of a control message from said first end-user terminal, check that said second end-user terminal has sufficient available resource to handle transmission from said first terminal, and may establish said second communications path, if said second terminal has sufficient available resource.
Said second end-user terminal may transmit a message containing an error code, to said first end-user terminal, in the event that said second end-user terminal has insufficient resource to handle transmission from said first terminal.
Short lived intra-LIS data transmissions may be transmitted over a pre-established default path established by a call initiating end-user terminal.
Long lived intra-LIS data transmissions may be transmitted over an SVC established by said a call initiating end-user terminal.
Short lived inter-LIS data transmission may be transmitted over said first communications path.
End-user terminals may detect and classify data flows as one of:
short lived intra-LIS;
long lived intra-LIS;
short lived inter-LIS; or
long lived inter-LIS.
ATM VCs may only be established for the transmission of long lived data flows.
Short lived data flows may be transmitted over a system default path by-passing address resolution and connection set-up procedures.
IP data may be transmitted over said first communications path prior to establishment of said second communications path.
An end-user terminal, or router, may multiplex a plurality of connections over a single VC.
Control messages may be processed in said routers.
Control messages may be processed in:
a router;
an ARP server; or
an end-user terminal.